This application relates generally to xerographic charging devices and more particularly to determining a pre-fault status condition in such charging devices.
Xerographic printing machines are known. It is known that some xerographic engines have a problem with frequent DC pin scorotron xe2x80x9cpin arcsxe2x80x9d. The root cause is believed to be as a result of pin and/or grid contamination. Contamination can be the result of fuser silicone oil volitles getting into the xerographic cavity, which form silica dendrites on the pins and/or grids of charging devices. There is also the and possibly of pin and/or grid contamination with paper dust, toner and or toner additives. Pin scorotrons are typically operated under closed loop feedback control with a constant current maintained between the pins and grid. The voltage required to maintain this constant current is called the xe2x80x9coperating voltagexe2x80x9d. Pin and/or grid contamination will cause a variation in this operating voltage. Furthermore the contamination can vary in its electrical conductivity as a function device operation history (powered/unpowered). This contamination conductivity variation is likely the root cause of the operating voltage variation.
When a pin to grid arc occurs, the print engine does an immediate hard-down, requiring clearing of the paper path, a time consuming job. The arc energy is high enough to disrupt communications, which can require a re-boot to restore the machine to operation. Regardless of the mature machine interval between arcs, it is advantageous to predict when a pin arc is likely to occur.
In a first aspect of the invention, there is described a method of determining a charging device pre-fault status, the charging device forming a charging device operating voltage that varies with time, the charging device comprising an included printing machine, the method comprising sampling the charging device operating voltage, forming a slope value based on a charging device operating voltage rate of change per unit time, and determining when the slope value falls in a charging device pre-fault status range of values.
In a second aspect of the invention, there is described a printing machine comprising a charging device, the charging device forming a charging device operating voltage that varies with time, the printing machine arranged to determine a charging device pre-fault status in accordance with a method, the method comprising sampling the charging device operating voltage, forming a slope value based on an charging device operating voltage rate of change per unit time, and determining when the slope value falls in a charging device pre-fault status range of values.
In a third aspect of the invention, there is described a method of forming a charging device service message based on a charging device operating voltage that varies with time, the charging device comprising an included printing machine, the method comprising sampling the charging device operating voltage, forming a slope value based on a charging device operating voltage rate of change per unit time, and forming a charging device service message when the slope value falls in a charging device pre-fault status range of values.
In a fourth aspect of the invention, there is described a method of triggering a cleaning cycle based on a charging device operating voltage that varies with time, the charging device comprising an included printing machine, the method comprising sampling the charging device operating voltage, forming a slope value based on a charging device operating voltage rate of change per unit time, and triggering a cleaning cycle in an included automatic cleaning system when the slope value falls in a charging device pre-fault status range of values.